Carbon Dots Derived from Coffee Residue for Sensitive and Selective Detection of Picric Acid and Iron(III) Ions

A facile method was developed to prepare carbon dots(CDs) by pyrolysis and etching of coffee residue. The as-prepared CDs show uniform spherical nanoparticles with an average size of 2.3 nm and exhibit excitation-dependent fluorescence emissions. Moreover, CDs also exhibit strong fluorescence quenching to nitro compounds and metal ions in both water and ethanol solutions, which could act as a platform for dual detection of PA(picric acid) and Fe3+ ions with low detection limits of 0.26 and 0.83 µmol/L, respectively. This work provides a novel method for preparation of environmental-friendly fluorescent CDs and shows their potential applications in photoluminescence sensors.